ABCG2 and colorectal carcinoma: ABCG2, which is a membrane‐associated protein, can relieve oxidative stress and the inflammatory response by inhibiting the NF‐κB signaling pathway, and the high expression of ABCG2 in CRC tissues may represent feedback of the overoxidative reaction, which is associated with a poor prognosis.56, 57 Most research has reported that inhibiting ABCG2, as a marker of chemoresistance in CRC, could enhance the efficacy of Hypericin‐mediated photodynamic therapy.